From 6535a148b592c1a5cabc34a9071209fb6a032790 Mon Sep 17 00:00:00 2001
From: "gcp-cherry-pick-bot[bot]"
 <98988430+gcp-cherry-pick-bot[bot]@users.noreply.github.com>
Date: Thu, 5 Jun 2025 16:00:22 -0600
Subject: [PATCH] Fix innermost brackets panic (cherry-pick #32120) (#32189)

Cherry-picked Fix innermost brackets panic (#32120)

Release Notes:

- Fixed a few rare panics that could happen when a multibuffer excerpt
started with expanded deleted content.

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
---
 crates/multi_buffer/src/multi_buffer.rs       |  2 +-
 crates/multi_buffer/src/multi_buffer_tests.rs | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/crates/multi_buffer/src/multi_buffer.rs b/crates/multi_buffer/src/multi_buffer.rs
index cbcedd543dc7528b23248a7782e2511e1c514df7..6a46bc6984085f8a04614cc6437369a8b5a8c3c2 100644
--- a/crates/multi_buffer/src/multi_buffer.rs
+++ b/crates/multi_buffer/src/multi_buffer.rs
@@ -6213,7 +6213,7 @@ impl MultiBufferSnapshot {
         cursor.seek_to_start_of_current_excerpt();
         let region = cursor.region()?;
         let offset = region.range.start;
-        let buffer_offset = region.buffer_range.start;
+        let buffer_offset = start_excerpt.buffer_start_offset();
         let excerpt_offset = cursor.excerpts.start().clone();
         Some(MultiBufferExcerpt {
             diff_transforms: cursor.diff_transforms,
diff --git a/crates/multi_buffer/src/multi_buffer_tests.rs b/crates/multi_buffer/src/multi_buffer_tests.rs
index 704c9abbe85bdac271535ecb3f7c66ec7002a7b4..435bfd56baa6da4585137867f7003704a12a2971 100644
--- a/crates/multi_buffer/src/multi_buffer_tests.rs
+++ b/crates/multi_buffer/src/multi_buffer_tests.rs
@@ -2842,6 +2842,22 @@ async fn test_random_multibuffer(cx: &mut TestAppContext, mut rng: StdRng) {
                 .unwrap()
                 + 1
         );
+        let reference_ranges = cx.update(|cx| {
+            reference
+                .excerpts
+                .iter()
+                .map(|excerpt| {
+                    (
+                        excerpt.id,
+                        excerpt.range.to_offset(&excerpt.buffer.read(cx).snapshot()),
+                    )
+                })
+                .collect::<HashMap<_, _>>()
+        });
+        for i in 0..snapshot.len() {
+            let excerpt = snapshot.excerpt_containing(i..i).unwrap();
+            assert_eq!(excerpt.buffer_range(), reference_ranges[&excerpt.id()]);
+        }
 
         assert_consistent_line_numbers(&snapshot);
         assert_position_translation(&snapshot);